Constant Gain Controller Research Articles

Active Control of Thermally Induced Vibrations in Smart Structure Instrumented with Piezoelectric Materials

In this paper, a finite element model of piezolaminated composite shell structure is developed using nine-noded degenerated shell element. The stiffness, mass and thermo-electro-mechanical coupling effect is incorporated in finite element modeling using first order shear deformation theory and linear piezoelectric theory. The sensor voltage is calculated using the same formulation and fuzzy logic controller is used to calculate the actuator voltage. The fuzzy logic controller is designed as double input-single output (DISO) system using 49 If-Then rules. The performance of fuzzy logic controller is compared with convention constant-gain negative feedback controller. The simulation results illustrate the superiority of fuzzy logic controller over constant-gain negative feedback controller.

A Self-Tuning Adaptive Controller for 3-D Image-Guided Ultrasound Cancer Therapy

One of the challenges in MRI-controlled hyperthermia cancer treatment for localized tumor is that the tissue properties are dynamic and difficult to measure. Therefore, tuning the optimal gains for a constant gain controller can be challenging. In this paper, a new multi-input single-output adaptive controller strategy is proposed to address these problems. The inputs to the controller block are the frequency, rotation rate, and applied power level of an interstitial applicator, and the output is the boundary temperature during treatment. The time-varying gains of the new controller are updated over time using Lyapunov-based stability analysis. The robustness of the new controller to changes in the parameters of the tissue is investigated and compared to a constant gain controller through simulation studies. Simulations take into account changes in tissue properties and other conditions that may be encountered in a practical clinical situation. Finally, the effectiveness of the proposed controller is validated through an experimental study.

Design of constant gain controllers for the hydraulic control system with a long transmission line

The paper presents the problems of describing the system of a pump-controlled motor with a long transmission line by means of a mathematical model with lumped parameters where the long transmission line is divided into n segments. The mathematical model thus obtained is of high order but its order is reduced by applying the appropriate methodology, which considerably increases its use value. A P controller was designed for that mathematical model of the system. The graphical method which includes performances (specification of damping of the system) and stability margins was used in the design. Thanks to strong software support, the complexity of synthesis of controllers was considerably reduced in comparison with the methods presented in the literature. Dynamic behavior of the closed loop system was treated in intensive simulation. The methodology applied provides significant energy savings.

Simulation Studies on Model Reference Adaptive Controller for Permanent Magnet Synchronous Motor Drive

Permanent magnet synchronous motor systems are usually used in industry. This kind of systems is nonlinear in nature and generally difficult to control. The ordinary linear constant gain controller will cause overshoot or even loss of system stability. Application of adaptive controller to a permanent magnet synchronous motor system is investigated in this paper. The dynamic model of the system is given and the stability is also analyzed using Popov's criterion. The steady state error can be eliminated using adaptive controller combined with an integration term. Simulation results show the performance of adaptive controller with fast response and less overshoot.

Model Reference Adaptive Control on a Hydraulic Servo System

Hydraulic servo systems are usually used in industry. This kind of system is nonlinear in nature and generally difficult to control. The ordinary linear constant gain controller can cause overshoot or even loss of system stability. Application of adaptive controller to a nonlinear hydraulic servo system is investigated in this paper. The dynamic model of the system is given and the stability is also analyzed using Popov's criterion. The steady state error can be eliminated using adaptive controller combined with an integration term. Simulation results show the performance of adaptive controller with fast response and less overshoot

Design of a modified linear quadratic regulator for vibration control of suspension systems

Abstract This paper is concerned with the construction of a prototype active vehicle suspension system for a one-wheel car model by using a modified Linear Quadric Regulator (LQR). The experimental system is approximately described by a non-linear system with two degrees of freedom subject to excitation from a road profile. The active control at the suspension location is designed by using feedback constant gain controller structure. The experimental results show that the active suspension system with LQR more improves the control performance than standard PID controller. On the other hand, the results improved that the modified LQR has superior performance for controlling suspension systems in real time.

Design of a Modified linear quadratic regulator for vibration control of suspension systems of military and civiL vehicle

Abstract The army and the people use many types of vehicles for industrial applications and military applications. This paper is proposed a construction of a prototype active vehicle suspension system for a one-wheel car model by using a modified Linear Quadric Regulator (LQR). The experimental system is approximately described by non-linear system with two degrees of freedom subject to excitation from profile different road disturbance profile. The active control at the suspension location is designed by using feedback constant gain controller structure. Furthermore, the experimental results show that the active suspension system with LQR more improves the control performance than standard PID controller. On the other hand, the results improved that the modified LQR has superior performance for controlling suspension systems in real time.

Multilayer neural networks-based direct adaptive control for switched nonlinear systems

This paper is concerned to present a direct adaptive neural control scheme for switched nonlinear systems with unknown constant control gain. Multilayer neural networks (MNNs) are used as a tool for modeling nonlinear functions up to a small error tolerance. The adaptive updated laws have been derived from the switched multiple Lyapunov function method, also an admissible switching signal with average dwell-time technique is given. It is proved that the resulting closed-loop system is asymptotically Lyapunov stable such that the output tracking error performance is well obtained. Finally, a simulation example of two Duffing forced-oscillation systems is given to illustrate the effectiveness of the proposed control scheme.

Adaptive Pitch Control of Variable-Speed Wind Turbines

The aerodynamic efficiency of a variable-speed wind turbine operating in Region 2, or below-rated wind speeds, is greatly affected by the identification of accurate parameters for the controller. In particular, the power coefficient (Cp) surface must be well known for optimal efficiency to be achieved with a constant-gain controller. However, adaptive control can overcome the inefficiencies caused by inaccurate knowledge of the Cp surface. Previous work focused on adaptive torque gain control to cause a variable-speed turbine to operate, on average, at the tip-speed ratio λ* for which the maximum Cp occurs. This paper considers the effects of adaptive blade pitch angle control on a turbine’s aerodynamic efficiency. Computer simulations and tests on a field turbine are used to verify the adaptive pitch control scheme. Simulation and field test results demonstrate that the adaptive pitch controller causes the pitch angle to approach its optimal value. Adaptive pitch control can be used to seek the optimal pitch angle for energy capture in Region 2 operation. Additional field operation is required before a statistically significant improvement in energy capture can be demonstrated.

Effect of the sampling rate of the tracking system on free-space laser communications

Lasers play an ever-increasing role in aerospace communication systems by providing the most logical connectivity channels. They drive the advancements in modern optoelectronics; however, successful implementation of this technology hinges on having an equally advanced beam-steering system for tracking the communication counterpart in the presence of complex maneuvers and the resident vibration of the airframe. The work presented in this paper concentrates on the development of agile acousto-optic beam-steering systems for laser communication terminals, which use constant-gain controllers augmented with an adaptive Kalman filter. Experimental results are presented to demonstrate communication performance as a function of the sampling rate in the tracking loop.

Fractional Order Filter Enhanced LQR for Seismic Protection of Civil Structures

This study presents fractional order filters to enhance the performance of the conventional linear quadratic regulator (LQR) method for optimal robust control of a simple civil structure. The introduced filters modify the state variables fed back to the constant gain controller. Four combinations of fractional order filter and LQR are considered and optimized based on a new performance criterion defined in the paper. Introducing fractional order filters is shown to considerably improve the results for both the artificially generated ground motions and previously recorded earthquake data.

An LTP/LPV approach to orbit control of spacecraft on elliptical orbits

The problem of orbit control for spacecraft on elliptical orbits is analysed and an approach to the design of optimal constant gain controllers for the periodic dynamics of relative motion is proposed. In particular, it is shown how the proposed approach can guarantee closed loop stability and optimal performance both in the case of circular and elliptical orbits.

Active Tiltrotor Whirl-Flutter Stability Augmentation Using Wing-Flaperon and Swash-plate Actuation

The effectiveness of active control employed via actuation of a wing trailing edge flap (wing-flaperon) and the rotor swashplate is examined for improving the whirl-flutter stability characteristics of the semi-span model of the XV-15 tiltrotor, over a wide range of conditions including variations in forward airspeed and operating RPM. Limits are enforced on the magnitude of control gains utilized based on assumptions on the maximum allowable flaperon/swashplate deflection and the expected magnitudes of disturbances experienced by the model. Full-state feedback, linear quadratic regulator (LQR) optimal controllers that are scheduled with respect to airspeed and RPM show significant improvement in the stability characteristics. However, constant-gain controllers and output-feedback controllers are appealing due to their simplicity; and the performance of such controllers (designed using a moving-point optimization scheme) are examined in terms of their robustness to variations in RPM and airspeed. Results show that for wing-flaperon actuation, constant gain (non-scheduled) full-state feedback controllers are robust over a fairly wide RPM range and increase critical whirl flutter speeds by as much as 90 knots at the cruise RPM, over baseline. Using output feedback of wing-states is as effective as fullstate feedback. For swashplate actuation constant-gain, full-state feedback controllers are robust over an even wider RPM range and increase the whirl flutter speed by as much as 75 knots at the cruise RPM. However, with swashplate actuation, feedback based on wingstates alone shows a reduced robustness to variation in RPM, suggesting that measurement or estimation of certain rotor states might be necessary. However, if the swashplate actuation limits are increased from a nominal value of ± 1 deg to ± 2 deg, control based on wing-state feedback is robust to large variations in RPM (over a range including both the cruise and the hover RPM of the XV-15).

Six-Axis Magnetic Levitation and Motion Control

This paper presents the development of a compact six-axis magnetic levitation stage, including the design and implementation of magnetic actuators, laser interferometer motion sensors, and motion controllers. The designed travel volume of the stage is 2times2times2 mm in translation and 4degtimes4degtimes4deg in rotation. A two-axis linear actuator, based on the magnetic Lorentz force law, was designed, and three two-axis actuators, equivalent to six single -axis actuators, were implemented to achieve six-axis actuation. A high-resolution laser interferometer measurement system was implemented and employed to measure the six-axis motion of the stage, facilitating real-time feedback control. Feedback linearization, based on rigid-body dynamics of the levitated stage, and force distribution were implemented in a computer-controlled architecture so as to establish a decoupled dynamics between the six computed inputs and the resulting six-axis motions. Constant gain controllers were then designed and implemented, according to the concept of loop shaping, for each of the six axes, and high positioning stability, 1.1 nm root mean square (RMS) for x and 0.74 nm RMS for y, has been achieved. Experimental results are presented to illustrate positioning stability, system linearity, dynamic response invariance, nano stepping, multiaxis contouring, and large rotational motion

OPTIMAL ORBIT CONTROL OF SPACECRAFT ON ELLIPTICAL ORBITS

The problem of orbit control for spacecraft on elliptical orbits is analysed and an approach to the design of optimal constant gain controllers for the periodic dynamics of relative motion is proposed. In particular, it is shown how the proposed approach can guarantee closed loop stability and optimal performance both in the case of circular and elliptical orbits.

Nonlinear finite element analysis of laminated composite shells with actuating layers

Nonlinear finite element analysis of laminated composite shell structures with smart material laminae is presented in the study. Third-order shear deformation theory based on Sanders nonlinear shell kinematics is chosen for the shell formulation and it is used to study deflection suppression characteristics of laminated composite shells. The smart material used in this study to achieve damping of transverse deflection is a magnetostrictive material, Terfenol-D, with a linear constitutive model. A negative velocity feedback control is used with a constant control gain. Newmark's time integration scheme and Newton–Raphson iteration method are used to solve the resulting nonlinear equations. A number of parametric studies are carried out to understand the damping characteristics of laminated composite shells with embedded smart material layers.

Adaptive Control Strategy for the Dynamic Positioning of a Shuttle Tanker During Offloading Operations

In deep water oil production, Dynamic positioning systems (DPS) strategy has shown to be an effective alternative to tugboats, in order to control the position of the shuttle tanker during offloading operations from a FPSO (floating production, storage, and offloading system). DPS reduces time, cost, and risks. Commercial DPS systems are usually based on control algorithms which associate Kalman filtering techniques with proportional-derivative (PD) or optimal linear quadratic (LQ) controllers. Since those algorithms are, in general, based on constant gain controllers, performance degradation may be encountered in some situations, as those related to mass variation during the loading operation of the shuttle tanker. The positioning performance of the shuttle changes significantly, as the displacement of the vessel increases by a factor of three. The control parameters are adjusted for one specific draught, making the controller performance to vary. In order to avoid such variability, a human-based periodic adjustment procedure might be cogitated. Instead and much safer, the present work addresses the problem of designing an invariant-performance control algorithm through the use of a robust model-reference adaptive scheme, cascaded with a Kalman filter. Such a strategy has the advantage of preserving the simple structure of the usual PD and LQ controllers, the adaptive algorithm itself being responsible for the on-line correction of the controller gains, thus insuring a steady performance during the whole operation. As the standard formulation of adaptive controllers does not guarantee robustness regarding modeling errors, an extra term was included in the controller to cope with strong environmental disturbances that could affect the overall performance. The controller was developed and tested in a complete mathematical simulator, considering a shuttle tanker operating in Brazilian waters subjected to waves, wind and current. The proposed strategy is shown to be rather practical and effective, compared with the performance of constant gain controllers.

Active vibration control of composite laminated cylindrical shells via surface-bondedmagnetostrictive layers

Active vibration control of composite laminated shells has been studied via embeddedmagnetostrictive layers. Magnetostriction targets the coupled strains or stresses; hence itis very important to develop a layerwise theory for laminates to determine thecoupled strains and stresses accurately. The present layerwise theory satisfiesthe continuity conditions of transverse shear stresses and in-plane displacementsat the interfaces of neighboring layers. This higher order layerwise theory hasan advantage over the equivalent single layer theory and provides an intuitivelycorrect computational model, which follows Newton’s third law in perfect bondingconditions for laminated materials. The displacements of the layerwise theorycombine classical thin shell theory and the displacements caused by the transverseshear stresses which satisfy the condition of zero transverse shear stresses at thefree surface. Laminated composite shells with surface layers of magnetostrictiveTerfenol-D particles have been studied. The direct and converse effects of theseproperties of smart materials are exploited here. Negative velocity feedback andconstant gain controllers are used to achieve effective vibration suppression. Thenumerical results show that vibration suppression of the shell with magnetostrictivelayers can be achieved by negative velocity feedback constant gain controllers.

Augmented control strategies for radiant floor heating systems

A dynamic model of a radiant floor heating (RFH) system useful for control analysis is developed. The overall model consists of a boiler, distribution system, an embedded tube floor slab and building enclosure. The overall model is described by non-linear differential equations which were solved using finite numerical methods. Two control strategies for improving the temperature regulation in RFH systems are proposed. These are: a multistage on–off control and an augmented constant gain control (ACGC). Simulation results show that the multistage control maintains zone air temperature close to the setpoint better than the existing on–off control scheme does. Likewise, ACGC gives good zone temperature control compared to the classical proportional control. The ACGC is shown to be robust to changes in weather conditions and internal heat gains. The advantage of the control strategies proposed is that they eliminate the use of outdoor temperature sensors required in some existing control schemes. Being simple and robust, the proposed control schemes are good candidate controls for RFH systems. Copyright © 2002 John Wiley & Sons, Ltd.

Gain-Scheduled Adaptive Control for Seismically Excited Hybrid Structures

A nonlinear controller is developed using gain-scheduled adaptation for a six-story, base-isolated office building subjected to strong earthquakes. Several linearized models and a scheduled piecewise linear model of the structure are developed using a finite-element nonlinear model. Compensators are designed, based on the H∞ control design method using the linearized models. The family of designed compensators is then gain-scheduled. The selected scheduling variable is a combination of the interstory ductility and the measured earthquake magnitude. The performance and robustness of the gain-scheduled adaptive controller is extensively studied for a variety of earthquake records and uncertainties, ranging from structure parameter variations to controller hardware-related time delays. All controller simulations are performed using the detailed finite-element nonlinear structure model. A key advantage of the gain-scheduled adaptive controller, compared to a constant-gain controller, is the reduction of up to 40% in the applied control forces while maintaining the same closed-loop performance.